A shift toward Th2 cytokine production has been demonstrated during pregnancy and high dose estrogen therapy and is thought to be the primary mechanism by which estrogen suppresses the development of experimental autoimmune encephalomyelitis. However, low dose estrogen treatment is equally protective in the absence of a significant shift in cytokine production. In this study cytokine-deficient mice were treated with estrogen to determine whether a shift in Th2 cytokine production was required for the protective effects of hormone therapy. Estrogen effectively suppressed the development of experimental autoimmune encephalomyelitis in IL-4 and IL-10 knockout mice and in wild type littermate mice with a similar potency of protection. Significant disease suppression was also seen in IFN-γ-deficient mice. The decrease in disease severity was accompanied by a concomitant reduction in the number of proinflammatory cytokine- and chemokine-producing cells in the CNS. Although there was no apparent increase in compensatory Th2 cytokine production in cytokine-deficient mice, there was a profound decrease in the frequency of TNF-α-producing cells in the CNS and the periphery. Therefore, we propose that one mechanism by which estrogen protects females from the development of cell-mediated autoimmunity is through a hormone-dependent regulation of TNF-α production.

Low-dose estrogen (E2) treatment significantly inhibits the clinical signs and histopathological lesions of experimental autoimmune encephalomyelitis (EAE), and is being used in clinical trials to treat multiple sclerosis. To assess the role of intracytoplasmic estrogen receptors in mediating suppression of EAE, we studied mice with disrupted estrogen receptor-alpha (Esr1) and -beta (Esr2) genes. We demonstrate that the protective effect of E2 is abrogated in B6.129-Esr1(tm1Unc) mice (Esr1-/-) but not in B6.129-Esr2(tm1Unc) mice (Esr2-/-). The loss of E2-mediated protection from EAE in Esr1-/- mice immunized with the encephalitogenic MOG-35-55 peptide was manifested phenotypically by the development of severe acute clinical signs and histopathological lesions even in the presence of moderately high serum E2 levels. This is in contrast to C57BL/6 wild-type (WT) mice and Esr2-/- mice in which E2 treatment resulted in comparable serum levels and markedly suppressed clinical signs of EAE and abolished inflammatory lesions in the CNS. This pattern showing a lack of E2-dependent inhibition of EAE in Esr1-/- mice was mirrored by an enhanced rather than a reduced secretion of TNF-alpha, IFN-gamma, and interleukin (IL)-6 in MOG-specific splenocytes and a lack of inhibition of message for inflammatory cytokines, chemokines and chemokine receptors in CNS tissue. These results indicate that the immunomodulatory effects of E2 in EAE are dependent on Esr1 and not Esr2 signaling.

Estrogen has been found to have suppressive effects on the induction of experimental autoimmune encephalomyelitis (EAE), an animal model for the human disease multiple sclerosis. We have investigated the effects of 17beta-estradiol (E2) treatment on dendritic cells (DCs) in two different mouse models of EAE. The frequency of CD11b(+)/CD11c(+) DCs was significantly decreased in the brain of mice protected from EAE induction by E2 treatment. In addition, the frequency of CD11c(+)/CD8alpha(+) DCs producing tumor necrosis factor (TNF)alpha and interferon (IFN)gamma in the spleen of E2-treated mice was dramatically decreased compared to that in control mice with EAE, demonstrating an effect of E2 on DC function. In order to examine E2 effects on DCs in more detail, splenic DCs were cultured in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4 to promote maturation. E2 pretreatment was found to suppress the ability of cultured DCs bearing a mature phenotype to present Ag to myelin basic protein (MBP)-specific T cells. Analysis of cytokine production demonstrated that E2 decreased TNFalpha, IFNgamma and IL-12 production in mature DCs. In addition, MBP-specific T cells cocultured with E2-pretreated mature DCs in the presence of antigen demonstrated a shift towards production of Th2 cytokines IL-4 and IL-10 and a concomitant decrease in the production of Th1 cytokines TNFalpha and IFNgamma. Thus, E2 treatment appears to have multiple effects on the DC population, which may contribute to a down-regulation or block in the activation of Th1 cells involved in the induction of EAE.

In a previous study, we demonstrated that myelin oligodendrocyte glycoprotein (MOG)-35-55 peptide could induce severe chronic experimental autoimmune encephalomyelitis (EAE) in HLA-DR2+ transgenic mice lacking all mouse MHC class II genes. We used this model to evaluate clinical efficacy and mechanism of action of a novel recombinant TCR ligand (RTL) comprised of the α1 and β1 domains of DR2 (DRB1*1501) covalently linked to the encephalitogenic MOG-35-55 peptide (VG312). We found that the MOG/DR2 VG312 RTL could induce long-term tolerance to MOG-35-55 peptide and reverse clinical and histological signs of EAE in a dose- and peptide-dependent manner. Some mice treated with lower doses of VG312 relapsed after cessation of daily treatment, but the mice could be successfully re-treated with a higher dose of VG312. Treatment with VG312 strongly reduced secretion of Th1 cytokines (TNF-α and IFN-γ) produced in response to MOG-35-55 peptide, and to a lesser degree purified protein derivative and Con A, but had no inhibitory effect on serum Ab levels to MOG-35-55 peptide. Abs specific for both the peptide and MHC moieties of the RTLs were also present after treatment with EAE, but these Abs had only a minor enhancing effect on T cell activation in vitro. These data demonstrate the powerful tolerance-inducing therapeutic effects of VG312 on MOG peptide-induced EAE in transgenic DR2 mice and support the potential of this approach to inhibit myelin Ag-specific responses in multiple sclerosis patients.